Dynamic recoil balancer for cyclic firing guns



Aug. 10, 1954 R. R. WALTON DYNAMIC RECGIL BALANCER FOR CYCLIC FIRING GUNS Filed Feb. 23, 1952 J72 van t0); Richard 1?. WkZtazz, v

Patented Aug. 10, 1954 -DY-NAIVIIC RECOIL' BALANCER FOR GYCLIC 2FI=BI NG GUNS .IGIClaims.

upon the theory'of snubbing-ther-recoil from each shot, Without regard to. cyclic: nature. of. the weapon. Thus,. the. Cuttszcompensator tendszto reduce the recoil 1 attendant .tupon each I shot. Similarly .the imountingi ofi tthe weapion upon I a very massive'rbasis" tends toi reduce the? ie'fiect' of vibrations by takingtup .the reactiomto". each shot in theiinertia oi a. very. heavy body.

While .these various expedientsfihave been: ef. fective' 'in greater and 1esser. de grees;.-itzhasmeen evident for many years that there twas: ample room ior further improvement. For: example, in: all automatici'weapons 1 presentlyiin use which have come to m'yattention the :muzzle :tends to rise and whipiduringf therfiringcof a:'ful1y=-automatic burst leading; to inaccuracy and diificulties of con-trolj. particularlyofshoulder weapons such as: the standard .45: caliber Thompson' maehine gun. -The accuracy ofthis particular gun is further impa'i red' because the bolt moves forward andioads a cartridge into the chamber after the tries ito iholdhthe gun down by: the-pistol grip.

Furthermore, with these weapons :of 7 higher power, including-:the IEO caIiher'rnachine gun and larger; the problem of:providing-suitablemountings t0 cushion the larzge tihr'atory iorces created byth recoii daecamevery important. i IIFOi'di a puch o s th mou tin ust'be rugged and very heavm thus not only increas-. ing the cost but likewise reducing portability and'whence the efiectiveness of the weapon for military uses. Where :problems of weight are concerned, as in military aircraft, theexceedingly heavy! mountings reduce the range and payload of the airplane.

:The' principal object :ofthe present invention is to :provide .az-novel andsimplified balancingate tachment for cyclic" firing rgunsiforrrovercoming most, .if not all, of" the foregoing shortcomings.

-"Another-. object of. the inventionis: toprovide a dynamic v.balancer .of the: type "described. which makes obsolete therroldenisnubbers.and'compensators,and which makes it possibiecgreatly toreducethe weight: of. the-carriageiin whichrthez gun is mounted.

Still another object of the inventionisrstotprovide .a" dynamic z-ba'lancer of the type .1 described whichwill tend: to improve theiaccuracyuof: the automatic weapon to. whiohzit iszappliedzto a'very marked degree.

Yet another object offlthe'invention is'to providea dynamie balancer which isapplicableto multiple barr'el cyclic :firingguns as wellzas to those having a single bar-rel.

In accordance": with the invention. I mount a Weight un -theautomatic-gun in such a manner that it is free to' slide' back and iorth generailly irr'the' direction or theline' of fire,=and preferably symmetrically arranged with respect 'to the barrel'or system of barrelsof the-gun. '-The=-w'eight is resiliently" coupled to thegunby means 'of a-sp'ring, "Thegun for 'the purposes of the-inveriticn iscorisidered' as a single rnass resiliently coupled-"through the spring to -the weight, and hence'the' three together constitute a spring-mass Vibratory s y-stem;- energizecbby the recoilof the gun and Pab1e ofpre agiju stment or tuning in thefield-so as-tohave a natural periodnof'vibration-oorresponding' to the rateof fire. Under these conditions the Weight, which represents only a sniallfraction of the-Weight of thegun, reciprocatesat the same frequency but in opposition-tdthe-movement of the gun itself. "Thus when thegun isrnoving to therearftheweight will be mo 'vingj' forwardlyagainstthe force of the spring-andyieeversa. By appropriately selecting the-mass-of themo in'g-weight andthe stifiness-coeiiicient0f :the spring relation" to the mass of n I m: a e intimat -a resonant system in which the Weight moves back and forth with considerable amplitude while the amplitude of motion of the gumbecomes negligible.

Conveniently, with single barrel guns, the weight, according to the invention, may consist of a ring mounted to slide back and forth on the barrel. A simple helical spring, surrounding the barrel, is attached to the weight at one end and to a portion of the barrel or receiver at the other. Preferably, I provide means for adjusting the length of the spring after installation so as to permit tuning in th field to the resonant frequency of the system.

Where multiple barrel weapons are involved, according to the invention, preferably I mount the balancing weight at a location at the center of symmetry of the vibrating system. In other words, generally speaking, the weight should always be disposed so as to vibrate in a line which is not only parallel to the axis of the gun barrel but symmetrically arranged with respect thereto and, in weapons having more than one barrel this line should be equidistant from all barrels so that there will be no torsional effect upon the same by reason of the movement of th balancing weight. Thus, where the gun has two barrels, the weight may conveniently be slidably mounted upon a shaft located midway between and parallel to the same.

Still further objects, advantages and features of th invention will become apparent from the following detailed description of preferred embodiments thereof taken in connection with the accompanying drawings in which Fig. 1 is a side view, partially in section, of the barrel portion of a single barrel automatic weapon showing the novel recoil balancer of the invention mounted thereon; and

Fig. 2 is a plan view of a double barrel machine gun showing the mounting of the novel balancer between the two barrels.

Referring first to the embodiment of Fig. 1, the barrel of the weapon, which may be, for example, a shoulder type sub-machine gun or a .30 or .50 caliber machine gun, is indicated by the number I0. Mounted to slide on the barrel is a generally cylindrical weight I2 haying a central bore I4. The outer surface of the barrel I is adapted to fit within the bore I4 to permit relatively undamped reciprocation of the weight I2 in the direction indicated by the arrow. At the rear end of the weight I2 there is a cylindrical extension I6 of reduced external diameter which is externally threaded, as shown, to hold the end coils of a helical spring I8 which also surrounds the barrel I0 and has its opposite end attached to a sleeve 20 which is located near the receiver end of the weapon. This sleeve 20 is provided with a helical groove 22, also adapted to receive coils of the other end of the spring I8. Preferably, the groove 22 is of greater length than is theoretically required by the construction to permit tuning adjustments in the field. Also preferably, the sleeve 20 is provided with a notch or marker 24 which may be used as a reference point in tuning.

Under ideal conditions of operation of the embodiment of Fig. 1 according to the invention, the natural period of vibration of the spring I8, mass I2 and gun will correspond to the rate of fire of the gun. Under such conditions the weight I 2 will move toward the muzzle of the gun while the barrel I0 is moving to the rear but with much greater amplitude, as indicated by the laws of motion. By I-Iookes Law for onedimensional motion we know that where a: is the change in length of the spring from its normal length by reason of the relative movement of the parts, is is its stiffness coefiicient, and F will be the force which the spring exerts at its ends. Further, we know that the force exerted by the smaller mass I2, accelerating through a greater distance, will balance the corresponding force exerted by the heavier mass of the barrel and other members accelerating in the opposite direction but with less amplitude. If the mass I2 is sufficiently small with respect to the mass of the barrel I0 and associated parts, then the motion of the mass I2 will be relatively large and the motion of the gun will be virtually negligible. I have found that, generally speaking, the ratio of the mass I2 to that of the gun should be not greater than approximately 1:5. It is evident, for example, that if the masses were the same (a ratio of 1:1) the amplitude of motion of each would likewise be the same, thus defeating the purpose of the balancing system. On the other hand, if the ratio of mass of the balancing weight I2 to that of the gun is made too small, the necessary amplitude of motion of the balancing weight would be excessive for a practical device. Therefore, it is possibleto give purely practical (but not theoretical) limits of this ratio as approximately from 1:5 to 1:20. A ratio of 1:10 yields good results.

From the foregoing principles, which have been only briefly outlined since they may be found in standard works on mechanics, it will be evident that the required mass of the weight I2 and the stifiness coefficient of the spring I8 may be calculated accurately by an appropriate mathematical treatment. However, in practice, I have found a simpler method yielding accurate results without involved computations. Knowing its normal rate of fire, the gun itself is attached to a suitable vibrator (a number of which are readily available on the market) and caused to reciprocate at this normal frequency linearly in the same direction it would have if firing. The amplitudes of vibration of the mass I2 and gun may then be observed by means of a stroboscope or other suitable instrument. The stiffness coefiicient of the spring I8 is adjusted by turning it in the groove 22 until the amplitude of the, mass I2 is at amaximum and the amplitude of the gun at a minimum. The position of the. rearmost coils of the spring may then be marked with reference to the reference marker 24 and the spring may always thereafter be adjusted to that point without further experimentation. During the compression and tension of the spring, its diameter decreases and forms avery secure method of fastening upon the projection I6 and the sleeve 29.

This experimental method of tuning obviates certain theoretical difficulties which might arise in calculating the values mathematically from the acceleration of the bolt and other working parts of the gun.

Turning now to Fig. 2, I have there shown a twin barrel machine gun having barrels 3B and 32 spaced from and parallel to each other. The balancer of the invention is mounted midway between the barrels 30 and32 by means of a shaft 38 held on brackets 34 and 36 which span the distance between the two barrels, one near the muzzle and the other near the breech. Shaft. 38 is held parallel to the barrels and the weight 49 is adapted to slide thereon. The weight 40 has a forward projection 42 which is spirally grooved (like the projection IS in Fig. 1) to hold the end dynamic recoil balancer comprising a weight having a central bore, said weight being slidably mounted by means of said bore on the barrel of said gun for relatively undamped longitudinal reciprocatory motion relative thereto, said weight having, a mass representing only a small fraction of that of said gun, a helical spring surrounding said barrel and having one end afiixed to said weight and the other end afiixed to a portion of said gun, said weight, gun and spring constituting a spring-mass vibratory system energized by the recoil of said gun and having a natural period of vibration corresponding to the rate of fire thereof with said weight and said gun reciprocatingv at the same frequency but in opposition to each other, the amplitude of motion of said weight being substantially greater than the corresponding amplitude of said gun, and mechanism for adjusting the stiffness coefiicient of said spring for tuning said systemto resonance.

7. In combination with a cyclic firing multiple barrel gun, a dynamic recoil balancer comprising a shaft mounted near the center of symmetry of said barrels and parallel thereto, a weight having a central bore slidably mounted by means of said bore on said shaft for relatively undamped longitudinal reciprocatory motion relative thereto, said Weight having a mass representing only a small fraction of that of said gun, and a spring connecting said weight to a portion of said gun, said weight, gun and spring constituting a springmass vibratory system energized by the recoil of said gun and having a natural period of vibration corresponding to the rate of fire thereof with said weight and said gun reciprocating at the same frequency but in opposition to each other, the amplitude of motion of said weight being substantially greater than the corresponding amplitude of said gun.

8. Apparatus in "accordance with claim 7 including mechanism for adjusting the stifi'ness coefficient of said spring for tuning said system to resonance.

9. In combination with a cyclic firing gun, a dynamic recoil balancer comprising a weight having a central bore slidably mounted by means of said bore on the barrel of said gun for relatively undamped longitudinal reciprocatory motion relative thereto, said weight having a mass representing only a small fraction of that of said gun, said weight also having a cylindrical projection at the rear end thereof and said barrel having a corresponding cylindrical sleeve thereon, said projection and said sleeve having external spiral grooves, and a helical spring surrounding said barrel with one end gripping said projection and the other end gripping said sleeve by means of said grooves, said weight, gun and spring constituting a. spring-mass vibratory system energized by the recoil of said gun and having a natural period of vibration corresponding to the rate of fire thereof with said weight and said gun reciprocating at the same frequency but in opposition to each other, the amplitude of motion of said weight being substantially greater than the corresponding amplitude of said gun.

10. Apparatus in accordance with claim 9 in which said spring is arranged to be rotated in said grooves for adjusting the length thereof and thereby adjusting its stiffness coeiiicient for tuning said system to resonance.

11. In combination with a cyclic firing double barrelgun, a dynamic recoil balancer comprising a pair of longitudinally spaced brackets connecting said barrels to each other, a shaft mounted on said brackets midway between said barrels and parallel thereto, a weight having a central bore mounted by means of said bore on said shaft for relatively undamped longitudinal reciprocatory motion relative thereto, said Weight having a mass representing only a small fraction of that of said gun, and a helical spring surrounding said shaft and connecting one end of said weight to one of said brackets, said weight, brackets, shaft, gun and spring constituting a spring-mass vibratory system energized by the recoil of said gun and having a natural period of vibration corresponding to the rate of fire thereof with said weight and said other members reciprocating at the same frequency but in opposition to each other, the amplitude of motion of said weight being substantially greater than the corresponding amplitude of said gun.

12. Apparatus in accordance with claim 11 including mechanism for adjusting the stiffness coefiicient of said spring for tuning said system to resonance.

13. Apparatus in accordance with claim 12 in which said mechanism comprises a sleeve on said shaft and a cylindrical projection on said weight, said projection and sleeve having helical grooves receiving some of the coils of said spring, said spring being adapted to be turned in said grooves for adjusting the length thereof.

14. In combination with a cyclic firing gu operated by relative motion of the barrel and the other parts of the gun, a dynamic recoil balancer comprising a weight attachable to said gun, said weight having a mass representingonly a small fraction of that of said gun, mountings for mounting said Weight on said gun for relatively undamped reciprocatory motion relative thereto generally in the direction of the line of fire, and a spring connecting said weight to one of said other parts of said gun, said weight, gun and spring constituting a spring-mass vibratory system energized by the recoil of said gun and having a natural period of vibration corresponding to the rate of fire thereof with saidweight and said gun reciprocating at the same frequency but in opposition to each other, the amplitude of motion of said weight being substantially greater than the corresponding amplitude of said other parts of said gun and the relative motion between said barrel and said other parts being unimpaired.

15. Apparatus in accordance with claim 14 in Which said weight is slidably mounted on' said barrel and said gun is provided with a sleeve in which said barrel is free to reciprocate, said sleeve constituting the part of said gun to which said spring is connected.

16. In combination with a cyclic firing gun operated by relative motion of the barrel and other parts of said gun, a dynamic recoil balancer comprising a weight having a central bore, said weight being slidably mounted by means of said bore on the barrel of said gun for relatively undamped longitudinal reciprocatory motion relative thereto, said weight having a mass representing only a small fraction of that of said gun, said gun having a sleeve surrounding a rearward portion of said barrel and in which said barrel is free to reciprocate, a helical spring surrounding said barrel and having one end connected to said weight and the other end connected to said sleeve, said weight, gun and spring constituting a spring; mass vibratory system energized by the recoil of said gun and having a natural period of vibration corresponding to the rate of fire thereof with said weight and said gun reciprocating at the Number same frequency but in opposition to each other, 1,763,064 the amplitude of motion of said weight being 2,155,130 substantially greater than the corresponding 2,421,858 amplitude of said gun and the relative motion 5 between said barrel and. said other parts of said gun being unimpaired, and mechanism for ad- Number justing the stiffness coeificient of said spring for 243,786 tuning said system to resonance. 9721202 10 References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,757,244 Green May 6, 1930 15 Name Date Paton et a1 June 10', 1930 Hanel Apr. 18, 1939 Trimbach June 10, 1947 FOREIGN PATENTS Country Date Great Britain Nov. 30, 1925 France Aug. 23, 1950 

